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A174830 Odd numbers k such that k^2 is an abundant number. 5
105, 315, 495, 525, 585, 735, 945, 1155, 1365, 1485, 1575, 1755, 1785, 1995, 2145, 2205, 2415, 2475, 2625, 2805, 2835, 2925, 3045, 3135, 3255, 3315, 3465, 3675, 3705, 3795, 3885, 4095, 4305, 4455, 4485, 4515, 4725, 4785, 4845, 4935, 5115, 5145, 5265 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Submitted at the suggestion of T. D. Noe.

For any number k, the abundance of k^2 is an odd number.

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..1000 from T. D. Noe)

FORMULA

a(n) = sqrt(A156942(n)). - M. F. Hasler, Jan 26 2020

MATHEMATICA

fQ[n_] := Block[{ds = DivisorSigma[1, n^2] - 2 n^2}, ds > 0 && OddQ@ ds]; Select[ Range[1, 5353, 2], fQ@# &]

PROG

(PARI) is(n)=n%2 && sigma(n^2, -1)>2 \\ Charles R Greathouse IV, Feb 21 2017

(PARI) [2*k-1|k<-[1..6e3\2], sigma((2*k-1)^2, -1)>2] \\ M. F. Hasler, Jan 26 2020

CROSSREFS

Cf. A033880, A156942.

Sequence in context: A046299 A010090 A306122 * A325312 A147576 A145752

Adjacent sequences:  A174827 A174828 A174829 * A174831 A174832 A174833

KEYWORD

nonn

AUTHOR

Robert G. Wilson v, Mar 30 2010

EXTENSIONS

Name corrected by T. D. Noe, Jul 09 2010

STATUS

approved

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Last modified May 19 05:04 EDT 2022. Contains 353826 sequences. (Running on oeis4.)